What do you think is a satisfactory response to external world skepticism? I'm having a hard time finding one I can accept.

The external-world skeptic purports to show that I can't know any external-world proposition P. How about this response?

1. Conceptual analysis reveals that knowledge is nothing more than reliably produced true belief, where reliability falls far short of logical infallibility.

2. If knowledge is nothing more than reliably produced true belief, then the skeptic's sensitivity condition on knowledge is false: I can have a reliably produced true belief that P, and hence knowledge that P, even if I would falsely believe that P if I were being deceived by an evil demon. (Analogy: My gas-engine car can be reliable even if it wouldn't work at all if it were on the airless surface of the moon.)

3. In particular, I can have a reliably produced true belief, and hence knowledge, that I'm not being deceived by an evil demon even if, were I being deceived by an evil demon, my belief that I'm not being deceived would not be reliably produced.

The skeptic then predictably asks: "But how do you know that your belief of P was reliably produced?" If my proposed analysis is correct, that question goes to the issue of how I know that I know that P, and second-order knowledge (my knowing that I know that P) isn't required for my first-order knowledge that P.